1. Field of the Invention
This invention relates generally to client-server computing architectures and communication techniques. More particularly, the invention relates to a system whereby a mobile worker and a central server may maintain a virtually continuous connection without the need to maintain a physical connection continuously.
2. Description of the Related Art
The concept of a virtual connection has arisen in connection with telecommuting and related applications. Such a system is described in U.S. Pat. No. 5,764,639. A telecommuter dials into a server using a standard telephone line. The telecommuter""s modem and a modem controlled by the central server establish a connection therebetween. Once a connection is established, the telecommuter may access a computer connected to the server, read emails and receive phone calls and faxes. For example, if a customer attempts to call the telecommuter at work by dialing into a private branch exchange (PBX), the server will convert the incoming call to a packetized form, such as H.323, and redirect the call via the existing connection between the telecommuter and the server. Using this system, the telecommuter may access a computer at work, answer phone calls and answer emails. The telecommuter thus appears to be present in his or her office and thus has a virtual presence there. Note for this system to properly function, the telecommuter must stay connected to the server at all times. While this does not present a significant problem for local telecommuting, this solution is quite costly for long distance telecommuting. Likewise, this solution is very costly if the telecommuter is mobile and must maintain a virtual presence with the server using a cellular wireless connection. Furthermore, in some areas it may be difficult to maintain a wireless connection continuously. A lost connection may also prevent one from regaining access to the system until some period of time has passed. Some mobile workers require only intermittent access to the server, but find it too inconvenient to place a dial-in call and to log onto the system every time access is needed.
There is a need to provide mobile workers with various forms of virtual connectivity. Mobile workers differ from telecommuters in that while a telecommuter typically works from a single home location or remote office, a mobile worker moves from location to location during the course of a normal working day. An example of a mobile worker is a home-care professional. A home-care professional is a medical worker who periodically travels to visit with different sets of homebound patients according to their individual needs. The individual patients each have a set of medical records indicative of their medical histories. A patient""s medical record is preferably maintained as an interactive electronic document containing multiple parts. For example, the medical record indicates to the home-care professional precisely what procedures are to be performed and what medications are to be administered or otherwise given to the patient. Once the services are performed, the home-care professional must annotate the medical record accordingly. The medical record is updated to reflect the patient""s vital signs and other information related to patient progress. Also, a billing system takes note to track expendables and services rendered. For example, the patient may be billed per visit and each visit may involve the expenditure of billable resources such as medicines.
In the above scenario, a mobile worker must interact with a central server during the course of a day. The worker may wish to access the central server while visiting a patient. The worker may also wish to access the server from a location where only a wireless connection can be established. From a performance perspective, an ideal solution is to provide the mobile worker with a wireless connection from a remote unit to a central server. Such a wireless connection could be established via a high-powered radio connection with a broad area of coverage or via an existing cellular or personal communication system (PCS) network. Solutions using high-powered radio links have the disadvantage that costly spectrum may be required. Maintaining a link on a cellular or PCS system is expensive in that a continuous connection consumes billable airtime which is also very costly. From an airtime-cost perspective, an ideal solution would be to force the worker to create a connection, download or up load information, and work locally with data on the remote unit as often as possible. This solution is tedious, and while saving airtime costs, may actually represent the more costly solution when professional service costs are factored in. This method has the added disadvantage that when files are uploaded or downloaded the data must be synchronized in case another user has changed the data in parallel with the mobile worker. Alternatively, other users must be xe2x80x9clocked outxe2x80x9d of the file from the time the mobile user downloads it until it is finally uploaded with any changes made. This is the problem solved using semaphores in shared memory systems. In the context of the present invention, a xe2x80x9cfile semaphorexe2x80x9d is a semaphore used to lock a second user out of a file while a first user is using it. Due to the aforementioned reasons, in many applications forcing the worker to repeatedly connect, disconnect, upload and download information is unacceptable.
Some mobile networks have been constructed using what is known as cellular digital packet data (CDPD). In a CDPD network, a remote unit transmits a data packet on an unused analog channel. In this sense the mobile unit remains virtually connected to a CDPD communication server. Wireless airtime is only consumed when data is actually sent. A disadvantage to this approach is CDPD networks are not universally available. Cellular coverage is much more ubiquitous than CDPD coverage. Also, CDPD network subscribers must often pay high fees and hence CDPD may not represent the most economical solution.
In some systems such as packet switched network routers, offices make use of dial-out links. Dial-out links are useful when remote offices are separated by long distances. In such systems, when a packet must be routed from a first office to a second office, a call is placed to route the packet. The dial-out connection remains connected until a no-traffic condition is detected, indicating the line is no longer active. When the no-traffic condition is detected the connection is dropped until it is again needed. Dial-out links are thus used to reduce long distance fees associated with maintaining a constant connection, and represents a useful starting point for solving the foregoing problems relating to the establishment of a virtual presence of a mobile worker. Client-server protocols and fast automated connection strategies employing dial-out links are needed to provide new ways for a mobile worker to maintain a virtual presence. Also, new methods are needed to enable dial-out links to be set up with low delays to make them more useful for novel systems.
It would be desirable to provide a system whereby a remote worker could maintain a seamless connection with a central server without the need to maintain a dedicated channel. It would be desirable if the remote worker could communicate with the central server without the need to spend time to enter a password, reconnect, and wait for a line negotiation sequence to proceed before being able to use the connection. It would be desirable for a protocol stack to activate a virtual session based on a prediction derived from a workflow. It would be desirable to use this prediction to set up a connection in the background without disturbing the mobile worker while the mobile worker performed tasks in a workflow. It would also be desirable to have a remote unit which contains most of the screen-related information needed to provide the appearance of an established connection before the connection has been fully established. It would be desirable for the remote unit to download information before it is needed and upload information after it is gathered without the user even being aware these actions are being performed. It would further be desirable to establish a virtual session using a first communication medium such as a landline and to later communicate using the same virtual session using a second communication medium such as a wireless link. This would allow a mobile worker to select the most economical or convenient means of communications at a given time. In embodiments involving modem-based connections, it would be desirable to transmit data immediately using instantly available but lower line speeds. It would be desirable to then negotiate a higher line speed in the background while the remote worker and/or the server perform other tasks. Moreover, it would be desirable to establish a session between a remote unit and a server so that various forms of communications may proceed while providing the user with the appearance the user is continuously connected to the server and has a virtual presence with the server.
The present invention solves these and other problems by providing systems and methods to enable a remote worker to stay virtually connected to a central server without the need to continuously remain connected via a physical channel. The present invention is useful when costs are associated with maintaining a connection, for example when the connection has associated with it long distance, wireless, or other usage-related toll charges.
A first aspect of the present invention involves a communication protocol making use of a virtual session layer. The virtual session layer allows a communication session and an application session to be maintained in a deactivated state when no physical connection exists. When a remote unit later reconnects with a server, the virtual session is placed into an active state and session communications resumes as though uninterrupted. A remote unit, a virtual session server, and a communication system including the remote unit and the virtual session server are presented to support virtual sessions communications. In one embodiment, the virtual session server manages a logon session between the remote unit and a server-side application program. The virtual session server emulates the presence of the remote unit to the server-side application program and thereby maintains the logon. In related embodiments, the server-side application program involves a communication server capable of relaying messages and establishing communication channels with the remote unit using the virtual session layer.
A second aspect of the present invention involves a method of accessing a central server from a remote unit. A first step involves presenting a workflow to a user via a user interface. A second step involves predicting, based upon the workflow, when the user will require connectivity to the central server. Based upon the prediction and in the background, a third step involves initiating the establishment of a physical layer communication connection to the central server.
A third aspect of the present invention involves a method of establishing a connection with a low connection set-up time. In a first step, the method initiates the establishment of a communication connection to be used to communicate with a remote entity. Next the method communicates application layer data via the communication connection prior to the completion of a line-rate negotiation process. Next the method negotiates a line speed in the background.
A fourth aspect of the present invention involves a method of setting up and operating a virtual session. This method can be practiced by a client-side remote unit or a server-side virtual session server. A first connection is established to a remote entity. This first connection is then used to establish a set of parameters needed to define a communication session with the remote entity. Next the first connection disconnected and a set of communication session parameters are maintained. Next a second connection to the remote entity is established and an authorization sequence is communicated. The communication session is next reactivated using the communication session using the second connection. A related method is used to allow a remote unit to maintain a virtual communications presence with a remote communication server coupled to a virtual session server.
A fifth aspect of the invention involves a method of accessing a server from a remote unit. At a first time, a first physical layer is used to establish a session with the server. The session involves a communication path that involves at least partially the first physical layer. The first physical layer is then decoupled while maintaining the session. At a second time, a second physical layer is used to resume the session so that the communication path of the session involves at least partially the second physical layer. At least one of the physical layers involves a local coupling to a local interface unit that couples to a WAN via a landline connection and the communication path of the session to the server comprises the landline connection.
Another aspect of the invention involves a method of reconnecting a telephone modem with a reduced delay by reducing a time associated with retraining. A first communication connection over a wireline telephone communication channel is initialized using the telephone modem. The initializing is performed at least partially by performing a line rate negotiation sequence with a far end modem to train a set of parameters to be used to support communications over the wireline telephone communication channel. The set of parameters can include signal constellation parameters, echo canceller coefficients, and/or equalizer coefficients for example. The set of parameters are then stored in a memory structure. Communication then commence at a negotiated date rate via the first communication connection with the far end modem using the parameters. Then the first communication connection is terminated. Next, the parameters are accessed from the memory structure and are used to at least partially initialize a second communication connection over the wireline telephone communication channel using the telephone modem. Communicaiton next commences at the negotiated date rate via said second communication connection by reusing at least some of the parameters. This allows a setup delay time associated with the initialization of the first communication connection to be longer than a setup delay time associated with the initialization of the seocnd communication connection.